1. Field of the Invention
This invention relates to the antihypertensive agents prazosin and trimazosin and their pharmaceutically acceptable acid addition salts and their use in treating congestive heart failure and ischemic heart disease.
2. Description of the Prior Art
Congestive heart failure, regardless of its etiology, is characterized by a distention of the myocardial tissue of the left and/or right ventricles of the heart reducing the efficiency with which the blood is ejected into systemic and/or pulmonary circulations and results in elevated venous pressure, lowered cardiac output and peripheral and pulmonary edema. If left untreated the health of a patient with congestive heart failure could deteriorate to the point where the disease would be fatal.
While there are several medicinals available for the treatment of congestive heart failure, the most widely used is digitalis. As effective as digitalis is in the treatment of this disease, its use is limited because of its slow onset of action and the small difference between the maximum therapeutic and mininum toxic dose levels.
Ischemic heart disease is characterized by the obstruction of the major blood vessels which service the heart, resulting in a decreased oxygen supply to myocardial tissue. During physical stress the reduction in the myocardial oxygen supply results in extreme cardiac pain known as angina pectoris.
Although nitrates, such as nitroglycerin, are the drugs of choice as vasodilators in the treatment of ischemic heart disease, they suffer from a short duration of action.